1. Field of the Invention
The present invention relates to a tire curing metal mold for curing a tire, and a tire manufacturing method using the tire curing metal mold.
2. Description of the Related Art
A tire curing metal mold for curing a tire is structured by combining a plurality of mold portions, and is broadly classified into a two-piece type and a segmented type on the basis of a division aspect. In the latter, an annular mold portion brought into contact with a tread surface of the tire is structured by a plurality of sectors divided in a tire circumferential direction, and an inner peripheral surface of each of the sectors is provided with a bone portion for forming a groove portion, and a concave portion for forming a land portion comparted by the bone portion. The respective sectors are spaced from each other in a mold opened state, and get together in a mold clamp state so as to form an annular shape.
In this case, in the sector mentioned above, there are an integrally cast type sector in which an inner circumferential side portion is integrally formed, and a split type sector structured by incorporating a plurality of pieces in an inner circumferential side of a back segment. In the split type sector, as described in Japanese Unexamined Patent Publication No. 2006-159669, International Laid-Open Publication No. WO2003/008169 and Japanese Unexamined Patent Publication No. 7-186303, it is very important to adjust a gap between the pieces. In other words, if the gap between the pieces is not uniformly formed and a deviation is generated, a rubber overflows at a position where the gap is too large, and a burr is generated on the molded tread surface. Further, at a position where the gap is too small, an air existing between the inner circumferential surface of the sector and the tread surface is not properly discharged, and a shrink called as lights is generated.
Accordingly, conventionally, an elastic body such as a leaf spring, a coil spring or the like is interposed between the end surfaces in the tire circumferential direction of the piece, whereby it is possible to adjust the gap between the pieces. In Japanese Unexamined Patent Publication No. 2006-159669, International Laid-Open Publication No. WO2003/008169 and Japanese Unexamined Patent Publication No. 7-186303, there is described a mold open state in which the pieces are spaced from each other by an energizing force of the elastic body, and a mold clamp state in which the pieces come close to each other against the energizing force of the elastic body, and there is disclosed a structure for manufacturing the tire while adjusting the gap by uniformly increasing and decreasing the gap between the pieces in accordance with an opening and closing motion of the metal mold.
However, in the tire curing metal molds, since each of the pieces slides in the tire circumferential direction every opening and closing motion, it has been known that each of the pieces wears out early due to a friction between the pieces and a friction between the piece and the back segment so as to reduce a mold service life. Further, if a galling is generated at a time when the pieces slide, there is a case that the gap is not properly adjusted and the problem mentioned above is generated. In this case, the galling means a phenomenon that the piece catches on the adjacent piece or the back segment so as to stay.